CHAPTER   ONE

INTRODUCTION

1.1       Background

Medicinal plants, also called medicinal herbs, botanical drugs or natural drugs are plants that have similar properties as conventional pharmaceutical drugs (WHO, 2008). Humans have used them throughout history to either cure or lessen symptoms from an illness. A pharmaceutical drug is a drug that is produced in a laboratory to cure or help an illness. World Health Organisation (WHO) has defined medicinal plants as plants that contain properties or compounds that can be use for therapeutic purposes or those that synthesize metabolites to produce useful drugs (WHO, 2008). According to (John 2004), the term “medicinal plant” includes various types of plants used in herbalism ("herbology" or "herbal medicine"), and the use of plants for medicinal purposes, and the study of such uses.

The word “herb” has been derived from the Latin word, “herba” and an old French word “herbe”. Nowadays, herb refers to any part of the plant like fruit, seed, stem, bark, flower, leaf, stigma or a root, as well as a non-woody plant. Earlier, the term “herb” was only applied to non-woody plants, including those that come from trees and shrubs. These medicinal plants are also used as food, flavonoid, medicine or perfume and also in certain spiritual activities (Khan, 2016).

Plants have been used for medicinal purposes long before prehistoric period. Ancient Unani manuscripts Egyptian Papyrus and Chinese writings described the use of herbs.  Evidence exist that Unani Hakims, Indian Vaids and European and Mediterranean cultures were using herbs for over 4000 years as medicine. Indigenous cultures such as Rome, Egypt, Iran, Africa and America used herbs in their healing rituals, while other developed traditional medical systems such as Unani, Ayurveda and Chinese Medicine in which herbal therapies were used systematically (Khan, 2016).

According to WHO (2008), traditional systems of medicine had been widely practiced on many accounts, these include population rise, inadequate supply of drugs, prohibitive cost of treatments, side effects of several synthetic drugs and development of resistance to currently used drugs for infectious diseases and these have however led to increased emphasis on the use of plant materials as a source of medicines for a wide variety of human ailment (WHO, 2008). WHO estimated 80 percent of people worldwide relying on herbal medicines for some aspect of their primary health care needs (WHO, 2008). According to WHO (2008), around 21,000 species of plant have the potential for being used as medicinal plants.

Treatment with medicinal plants had been considered very safe as there is no or minimal side effects (Khan, 2016). These remedies are in sync with nature, which is the biggest advantage. The golden fact is that, use of herbal treatments is independent of any age groups and the sexes (Khan, 2016). Medicinal plants have been considered as a rich resources of ingredients which can be used in drug development either pharmacopoeial, non-pharmacopoeial or synthetic drugs. Apart from that, these plants play a critical role in the development of human cultures around the whole world (Khan, 2016). Moreover, some plants have been considered as important source of nutrition and as a result of that, they are recommended for their therapeutic values. Some of these plants include ginger, maize, green tea, walnuts, aloe, pepper and turmeric etc (Khan, 2016). Some plants and their derivatives are considered as important source for active ingredients which are used in aspirin and toothpaste etc (Khan, 2016).

Apart from the medicinal uses, herbs are also used in natural dye, pest control, food, perfume, tea and so on. In many countries different kinds of medicinal plants/ herbs are used to keep ants, flies, mice and flee away from homes and offices. Nowadays medicinal herbs are important sources for pharmaceutical manufacturing.

According to (Lai et al., 2004), Medicinal plants have many characteristics when used as a treatment, and they are considered as the following:

i.                    Synergic medicine: - The ingredients of plants all interact simultaneously, so their uses can complement or damage others or neutralize their possible negative effects.

ii.                  Support of official medicine:-In the treatment of complex cases like cancer diseases the components of the plants proved to be very effective.

iii.                Preventive medicine: - It has been proven that the component of the plants also characterize by their ability to prevent the appearance of some diseases. This will help to reduce the use of the chemical remedies which will be used when the disease is already present i.e., reduce the side effect of synthetic treatment. (Lai et al.,2004).

1.2       Botanical Classification of Zea mays

Zea mays can be classified as:-

Kingdom:                    Plantae

Subkingdom:               Tracheobionta – vascular plants

Superdivision:              Spermatophyta – Seed plants

Division:                      Magnoliophyta – Flowering plants

Class:                          Liliopsida

Subclass:                     Commelinidae

Order:                         Cyperales

Family:                        Poaceae – Grass family

Tribe:                          Andropogoneae

Genus:                         Zea L. – corn P

Species:                        Zea mays L. – corn P

COMMON NAMES

English:                       Corn or Maize

Ibibio:                          Akpakpa, Ibokpot

Figure 1: Diagram of Zea mays husk

 

             Zea mays                                                            Zea mays husk

Source: Shuttlestock.com

1.2.1    Habitat:

Zea mays can grow in light (sandy), medium (loamy), and heavy (clay) soils. Although it can thrive in many different types of soils. It requires that the soils are well-drained. Sweet corn prefers that the soils be slightly acidic or neutral. It cannot grow in the shade. Also, it needs a cultivated bed of soil to thrive. Zea mays requires nitrogen, phosphorus and potassium to thrive. These nutrients are generally attained through chemical fertilizers or manure. They are added usually before plowing, at planting time or as the plants grow. Sweet corn begins to develop within two to three days after it is planted.

1.2.2    Description of Zea mays

            According to the studies carried out by   (James 1983) Zea mays is a vigorous annual grass, varying greatly in size according to race and growth conditions; and it is believed to have originated in Mexico in prehistoric times. It is now distributed over the world and grown wherever summers are reasonably warm .Zea mays can also be described as monoecious plant. Male flowers in terminal racemes; spikelets, two-flowered glumes nearly equal, herbaceous, terminating in two sharp points; females, axillary in the sheaths of the leaves. The spikes or ears proceed from the stalls at various distances from the ground, and are closely enveloped in several thin leaves, forming a sheath called the husk; the ears consist of a cylindrical substance, a pith called the cob; on this the seeds are ranged in eight rows, each row having thirty or more seeds. From the eyes or germs of the seeds proceed individual filaments of a silky appearance and bright green colour; these hang from the point of the husk and are called 'the silk.' The use of these filaments or stigmata is to receive the farina which drops from the flowers, and without which the flowers would produce no seed. As soon as this has been effected, the tops and 'the silk' dry up. The maize grains are of varying colour - usually yellow, but often ranging to black (Duke 1983).

1.2.3    Chemical and Phytochemical Constituents of Zea mays

According to Dong et al.,( 2014) Eight phenolic compounds ( gallic acid, protocatechuic acid, chlorogenic acid, cafeic acid, femlic acid, rutin, resveratrol, and kaemferol) have also been detected in ethanol extract of Zea mays husk (Dong et al., 2014). Anthocyanin has been reported to be present in purple corn husk. The main components of purple corn husk anthocyanin were cyanidin derivatives, and the most prevalent constituents were cyanidin-3-glucoside, cyanidin-3-succinylglucoside and perlargonidin-3-(6’’-malonylglucoside) (Li et al., 2008). Also Phytochemical compounds with antifungal activity such as 6-mehoxybenzoxazolinone and 6,7-dimethoxybenzoxazolinone, and (6R)-7,8-dihydro-3-oxo-a-ionone and (6R; 9R)-7,8-dihydro-3-oxo- a-ionol were isolated from root extract and root exudates of Zea mays (Park et al.,2004).

1.2.4   Medicinal Uses of Zea Mays

According to (Duke and Wain., 1981), the medicinal uses of  Zea mays includes the following;

(i)           An infusion of the parched corn allays nausea and vomiting in many diseases. Corn meal makes a palatable and nutritious gruel and is an excellent diet for convalescents, Cancer; Hypoglycemic; Hypotensive; Lithontripic; Vasodilator; Warts.

(ii)         A decoction of the leaves and roots is used in the treatment of strangury, dysuria and gravel.

(iii)       The corn silks are cholagogue, demulcent, diuretic, lithontripic, mildly stimulant and vasodilator. They also act to reduce blood sugar levels and so are used in the treatment of diabetes mellitus as well as cystitis, gonorrhea, gout, gallstones and urinary troubles( Foster and Duke, 1990). The silks are harvested before pollination occurs and are best used when fresh because they tend to lose their diuretic effect when stored and also become purgative.

(iv)        A decoction of the cob is used in the treatment of nose bleeds and menorrhagia.

(v)          The seed is diuretic and a mild stimulant. It is a good emollient poultice for ulcers, swellings and rheumatic pains, and is widely used in the treatment of cancer, tumors and warts. It contains the cell-proliferate and wound-healing substance allantoin , which is widely used in herbal medicine (especially from the herb comfrey, Symphytumofficinale) to speed the healing process.  

(vi)        The husks are also used in treatment of rheumatic pains (Owoyele et al., 2010).  It is also taken as warm tea for the treatment of malaria and diabetes in Ibibio traditional medicine (Okokon et al; 2017).

1.2.5    Economic importance of Zea mays

            Zea mays L. is said to be the most important grain in Africa and it is usually produced   throughout diverse environment. Maize also known as corn is a cereal grain first domesticated by indigenous peoples of Southern Mexico about 10,000 years ago (Franklin, 2013). The leafy stalk of the plant produces separate pollen and ovuliferous inflorescences or ears, which are fruits, yielding kernels or seeds. Maize is consumed in developed countries mainly as second-cycle produce, in the form of meat, eggs and dairy products. Maize has become a staple food in many parts of the world, with total production surpassing that of wheat or rice.

1.2.6    Biological activities of Zea mays

The biological activities reported on the husk extract includes; analgesic, anti-inflammatory   (Owoyele et al., 2010), antioxidant (Dong 2014), antidepressant (Okokon et al., 2016), antimalarial and antiplasmodial activities (Okokon et al., 2017).

1.2.7    Antidepressant Activity of the husk extract of Zea mays:

The husk extract was investigated for antidepressant activity. The Zea mays husk extract (187-748mg/kg) was found to increased significantly the line crossing, walling and rearing activities in open field test and reduced significantly the immobility time in force swimming test. The husk extract of Zea mays demonstrated prominent antidepressant activity which was due to the activities of its phytochemical constituents (Okokon et al., 2016).

1.2.8    Antioxidant Activity of Zea mays husk extract:

The antioxidant activities of the husk extract against [2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2’-diphenyl-1-picrylhydrazyl (DPPH) and 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) radical-scavenging activity, reducing, power, and ferric reducing-antioxidant power (FRAP) of the above extract were investigated by Dong et al.,(2014). The husk extract was found to exert significant antioxidant activity in all the models studied (Dong et al., 2014).

1.2.9    Antimalarial, Antiplasmodial and Cytotoxicity activities of the husk extract of Zea mays:

This study was carried out by Okokon et al, (2017).The Zea mays husk extract (187-749mg/kg, p.o) was found to exert significant antimalarial activity against Plasmodium  berghei  infections also exerted prophylactive and curative tests. The crude extract and fractions also exerted prominent activity against both chloroquine sensitive (Pf 3D7)  and resistant (Pf INDO) strains of Plasmodium falciparum with the ethyl acetate fraction exerting the highest activity with IC50 value of 9.31+0.46 μg/mL (Pf INDO)  (Okokon et al.,2017a). The crude extract and fractions were not cytotoxic to both HeLa and HEKS cell lines tested (IC50 of > 100 μg/mL) (Okokon et al., 2017a).

1.2.10  Antiplasmodial activity and Cytotoxicity of ethanol extract of Zea mays root:-

According to a study by Okokon et al. ( 2017b) on antiplasmodial activity and cytotoxicity of ethanol extract of Zea mays root, the crude extract of Zea mays root (45-135 mg/kg,p.o) showed  significant  antimalarial  activity  against Plasmodium berghei infection in suppressive, prophylactic and curative tests with a prolonged survival time. The crude extract was not cytotoxic to the two cell lines tested with TC50 of > 100 μg/mL against both Hela and HEKS cell lines.

1.2.11  Analgesic and Anti-inflammatory activities of Zea mays husk:

Anti-inflamamatory and analgesic activities have also been reported on the Zea mays husk  extract ( Owoyele et al.,  2010; Bamidele et al.,2010).

1.2.12  Analgesic and Anti-inflammatory activities of Zea mays leaves:-

The anti-inflammatory and analgesic activities of the leaves of Zea mays were also studied   by Okokon et al. (2016). The leaf extracts showed prominent anti-inflammatory and analgesic activities which were assumed to be due to its phytochemical constituents acting through anti-oxidant action and other mechanisms.

Okokon et al. (2016) also reported anti-nociceptive and anti-inflammatory activities of root extract of Zea mays. It was suggested that the effects of this root extract may in part be mediated through the chemical constituents of the part such as alkaloids, flavonoids, tannins, terpenes, saponins, anthraquinones, reducing sugars and cardiac glycosides.

1.2.13  Acute Toxicity

The intraperitoneal median lethal dose (LD50) of the crude husk extract was determined to be 1874.83 mg/kg in mice (Okokon et al., 2017a).

1.2.14 Anti-diabetic and Hypolipidemic activities of Corn silk extract:

Ghada et al., (2013) and Zhang et al., (2016) carried out studies on anti-diabetic and hypolipidemic activities of corn silk extract in Streptozotocin induced-diabetic rats. The corn silk extract was found to lower blood glucose level of the rats. Total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol level (LDL-C) were reduced and the high density lipoprotein cholesterol level (HDL-C) was increased.

1.2.15  The Anti-ulcer effect of Zea mays corn extract:

Jadhav (2016) determined in experimentally-induced gastric ulcer rats that the corn extract was capable of inhibiting lesion formation induced by ethanol, the gastro-protective effect of Zea mays corn extract may be mediated partly by preservation of gastric mucosal damage against acidic gastric content.

1.2.16  Anti-diabetic and Hypolipidemic activities of Zea mays husk extract and fractions:

Okokon et al., (2017) found out in their studies on anti-diabetic and hypolipidemic activities of Zea mays husk extract and fractions that treatment of alloxan-induced diabetic rats with the extract/fractions caused reduction in fasting blood glucose (FBG) of the treated diabetic rats in both acute and prolonged studies with dichloromethane fraction having the highest activity. The bio-activities of extract and fractions (n-hexane and dichloromethane) were higher than that of the standard drug. The extract/fractions also enhanced glucose utilization capacity of the diabetic rats causing increase in serum insulin levels. The husk extract and fraction further lowered serum total cholesterol, triglycerides, LDL-cholesterol, VDL-cholesteorl with increased HDL-cholesterol level in treated diabetic rats. Histology of pancreas revealed the absence or reductions in pathological signs in treated diabetic rats. The GCMS analysis of dichloromethane fraction revealed the presence of phytochemical compounds of pharmacological importance.

1.2.17 Hepatoprotective activity of Zea mays extract and fractions of husk against Alloxan-induced oxidative stress in diabetic Rats

A study on hepatoprotective activity of Zea mays extract and fractions of husk against alloxan-induced oxidative stress in diabetic rat was carried out by Okokon et al., (2017). It was reported that the husk extract and fractions of Zea mays   caused significant increase in the levels of oxidative stress markers (SOD, CAT, GPx, GSH) in the liver of the diabetic rats. The extract/fractions treatment caused reduction in liver enzymes (ALT and ALP), GGT, total bilirubin, and also increased total protein and albumin levels as well as AST. Histology of liver revealed absence or significant reductions in pathological features in the treated diabetic rats compared to untreated diabetic rats. The GCMS analysis of n-hexane fraction revealed the presence of phytochemical compounds of pharmacological importance. The results shows that Zea mays husk extract and fractions possess hepatoprotective activity against alloxan-induced liver injury.

1.2.18 Nephroprotective activity of husk extract and fractions of Zea mays against Alloxan-induced oxidative stress in diabetic rats:

The husk extract and fractions was seen to cause significant increase in the levels of  oxidative stress markers ( SOD, CAT, GPx, GSH) in the kidney and MDA level was decreased in the treated diabetic rats (Okokon et al., 2017). Okokon et al., (2017) in the same study also found that the extract and fractions caused significant reduction of elevated serum levels of creatinine, urea and chloride in the diabetic rats. Histology of kidney revealed absence or significant reductions in pathological features in the treated diabetic rats compared to untreated diabetic rats. The GC-MS analysis of n-hexane fraction revealed the presence of phytochemical compounds of pharmacological importance. The results showed that the husk extract and fractions of Zea mays has antioxidative and nephroprotective potentials which may be due to antioxidant activities of their phytochemical constituents (Okokon et al., 2017).

1.3       Aim and Objectives of the Study

1.3.1    Aim

Zea mays husk has been used locally for the treatment of gastrointestinal disorders such as ulcer. Based on this, the work was designed to investigate the anti-ulcerogenic potentials of the extract using experimental animal models.

1.3.2    Objectives of the Study

1.         To evaluate the anti-ulcerative activity of the ethanol extract of Zea mays husk in rats using various models.

2.         To examine the effect of various concentrations of ethanol extract of Zea mays husk on ulcer in rats.

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